1. Field of the Invention:
The present invention relates to a webbing lock apparatus for use in a seatbelt system designed to restrain an occupant of a vehicle when an emergency situation occurs, the apparatus being employed to clamp an intermediate portion of an occupant restraining webbing so that the webbing is locked in position. More particularly, the invention pertains to a webbing lock apparatus which is suitably incorporated in a webbing retractor disposed on the ceiling of a vehicle.
2. Description of the Prior Art:
A typical webbing retractor is arranged such that one end of an occupant restraining webbing is secured to a webbing takeup shaft, which is rotated by the biasing force of a spiral spring in such a manner as to wind up the entire or a predetermined length of the webbing. In general, the webbing retractor is secured to a side wall of the vehicle body, and the webbing portion which is wound off from the webbing takeup shaft is turned about at a slip joint so as to be used as a shoulder webbing.
This type of seatbelt system, however, suffers the following problem. Since the webbing is turned about at the slip joint with an acute angle, a disadvantageously large frictional resistence occurs between the webbing and the slip joint when the webbing is moved.
In order to overcome such a problem, a system has heretofore been developed in which the webbing retractor is installed on the ceiling of the vehicle or on its center pillar, and the webbing is wound off through an opening formed in a panel. With this system, although the course of the webbing is slightly changed at the panel opening, the turnabout angle of the webbing is not acute and, therefore, the frictional resistance occurring between the webbing and the opening is favorably reduced.
On the other hand, the webbing retractor generally incorporates a webbing lock apparatus which is designed to prevent the webbing from being wound off when a vehicular emergency occurs.
In U.S. patent application Ser. No. 686,395, for example, a webbing lock apparatus suitable for the webbing retractor mounted on the ceiling of the vehicle is shown, in which the webbing is clamped by a fixed lock member and a movable lock member when a vehicular emergency occurs. In the webbing lock apparatus, an acceleration sensor of a relatively large size is used since the webbing itself is pushed up by the inertial force of the acceleration sensor. Also, it has been expected to reduce a projection amount of the webbing lock apparatus from the ceiling of the vehicle.